If you're worried about your account, you can normally call up your bank to check. But not this time.Gordon Anthony McGowan/Flickr (CC)A cyber criminal raiding a target's bank account typically has a narrow window in which to operate. The moment the victim realises what's up, they'll contact their bank, locking the attacker out for good.

But one piece of malware has found a way to get around this — by blocking the victim from contacting the bank altogether.

Android.Fakebank is a piece of malware targeting Android smartphones. Once it gets onto your device, it tricks the victim into replacing any banking apps they have installed with fraudulent versions that grant the attacker access to the victim's funds.

First discovered by security firm Symantec in October 2013, it has now been updated with call-blocking functionality, the company says in a blog post. It monitors all the outgoing calls that the infected phone makes, and if any are to certain financial institutions, then they're automatically blocked. Even if you're worried about your account, you won't be able to call up your bank to make sure things are okay — giving the attacker more time in which to operate.

Pretty crafty.

The trojan in question targets people in South Korea and Russia, and banks in those countries — but similar malware could plausibly exist elsewhere in the world too. You can protect yourself by only downloading trusted apps from the official Google Play app store, and making sure your settings don't allow installation of apps from unknown sources (it should be set to block these by default).